SUMMARY: This project was designed to understand the role thyroid hormones play in growth and development of mouse mammary glands and to correlate these observations with tumor incidence. Studies include: 1) examination of the morphology of mammary glands during several developmental stages in euthyroid, hypothyroid and hyperthyroid mice; 2) evaluation of the ability of epithelial cells from these glands to differentiate in explant culture and elaborate the milk-proteins casein and alpha-lactalbumin under the influence of insulin, hydrocortisone, prolactin and thyroid hormones; 3) investigation of the characteristics of specific receptors for thyroid hormones and prolactin within the mammary tissue. BIBLIOGRAPHIC REFERENCE: Vonderhaar, B.K.: Studies on the Mechanism by which Thyroid Hormones Enhance alpha-Lactalbumin Activity in Explants from Mouse Mammary Glands. Endocrinology 100: 1423-1431, 1977.